1. Field of the Invention
The present invention relates to electrical generators, and more particularly to improvements in synchronous generators referenced to an AC signal.
2. Description of the Prior Art
In my prior U.S. Pat. No. 4,229,689, issued on Oct. 25, 1980, I have described a synchronous generator conformed for phase and frequency synchronized operation with the alternating signal of an AC power grid. This generator would then augment the power supplied by a central power station, like the electrical power produced by a public utility, with various local power sources such as windmills or water wheels. Augmentation of this kind matches the local power requirements with the local power available and thus matches the frequency and phase of the utility grid. The available local power, however, often varies in response to weather conditions and other local variables and a perfect match with the local demand is thus rare or more frequently non-existent. The utility grid thus provides, through averaging techniques, an effective power storage function against which power is drawn when the demand exceeds local supply and into which excess local power is transferred.
As a consequence a generator driven by a local, mechanical, power source will vary widely in rate, a variation heretofore less than fully resolved by inductive devices.
In the past, other portable generators typically took the form of an unregulated device producing electrical power at a frequency which depends on the mechanical input rate. Since this rate is often incompatible with the rate demanded by the device drawing the power, the typical approach has been either to constrain the generator to a governed rotational rate or to interpose an inverter fixed to a specific frequency. As a consequence the generator is often not optimized for its operating rate resulting in substantial losses in efficiency.
To a large extent the wide range of shaft rates has been accommodated in my prior U.S. Pat. No. 4,229,689. Nonetheless, the second order effects of induction present contraints on the efficiency and/or dynamic range which have led to further improvements described herein.
Simply, mechanical geometry and electromagnetic effects resolve themselves into various rate optima depending on detailed effects. The present generator lends itself uniquely to controlled response by which the physical constraints and geometry can be corrected out. Thus the complement of generator sizes can be conveniently reduced and, more importantly, the operating range of each size is substantially expanded.
Accordingly, a technique for expanding the operating range of synchronous generators is disclosed herein with particular reference to the teachings of U.S. Pat. No. 4,229,689.